Process of preparing mixed ester anhydrides



Patented Mar. 25, 1941 v UNITED STATES PATENT OFFICE PROCESS OF PREPARING IVHXED ESTER ANHYDRIDES No Drawing. Application April 14, 1937, Serial No. 136,833

10 Claims.

The present invention relates to improvements in the manufacture of organic compounds of the type of acid anhydrides. The invention also includes improvements in the recovery of such 5 compounds and the production of useful commercial products therefrom, and is a continuationin-part of Serial No. 556,940, filed August 13, 1931, Patent No. 2,099,909. I

The invention has for one of its principal ob- 10 jects a process of making acid anhyd-rides and mixed ester anhydrides by reacting ketene or its homologs or polymers with organic acids other than that corresponding to the ketene used, and separating the compounds so formed. Further objects of the invention will appear as the description proceeds.

Organic acids having more than two carbon atoms and having a boiling point above 130 C. upon being treated at ordinary temperatures 20 (such as 20 C.) with ketene, enter into a chemical reaction, which is generally manifested by the liberation of heat. The reaction which occurs consists in the addition of the ketene to the 25 organic acid with the resulting formation of an cording to the following equationi RCOOH+CH3CQ \O Clix-C I Add Ketene Mixed anhydride where R is an alkyl radical containing two or r more carbon atoms. The product so formed is relatively unstable,

beingeasily decomposed by heat to yield an organic anhydride and acetic anhydride, likely according to the following:

5 On subjecting the mixed anhydrid'e to heat and distillation at atmospheric pressure or at a pres- =surellower than atmospheric, acetic anhydride is separated in the form of a vapor, and is condemed. The residual acid anhydride obtained II in the distillation is removed as bottom It is 'benzylaniline, etc.

aceto-organic acid mixed anhydride, probably ac-.

more reactive than the corresponding acid and may be used directly to esterify hydroxy compounds such as alcohols, cellulose, glycols, etc. or to acyla'te amino compounds, such as aniline,

Neutral solvents, such as s ethyl ether, acetone, etc., may be used to keep the organic acid in solution, especially when the acids treated are solidsvor very viscous liquids. These solvents are generally recovered before the distillation of the acid anhydrides. Aliphatic, 10 cyclic or heterocyclic organic acids are used to react with ketene in the above reactions.

The method described above mentions the. treatment of a single organicacid. However, a mixture of two or more organic'acids may be treated in a like manner and after removal of the solvent-Land acetic anhydride, may be tractionated into the separate anhydrides, or used as a mixture of anhydrides. Polybasic acids may be used in alike manner.

Organic acids containing the hydroxyl or amino groups, upon treatment with ketene at ordinary temperatures form ester acids or mixed ester anhydrides. For instance, upon treating an organic hydroxy acid with ketene, the ketene first reacts with thehydroxyl group forming an ester acid and may then further add to the carboxyl group with the resulting formation or a mixed ester anhydride oi the organic hydroxy acid and acetic acid. .Upon heating, the relatively unstable mixed ester anhydride 0! the organic acid is decomposed to acetic anhydride and the corresponding ester anhydride. These are then separatedv by -distillation as described previously. The iollowing examples are given merely to illustrate the invention and are not to be regarded as limiting the invention in any respect. A solution or tartaric acid in acetone was treated at room temperature with gaseous ketene for six hours, after which the acetone was allowed to 40' evaporate oil. The product was a clear viscous -liquid consisting essentially of acetic ester of tartaric acid.

Rapid evolution of heat takes place during .such reactions and suitable cooling means are preterably provided to maintain substantially low temperature, below C. or at most 0., j and preferably the temperature is maintained at or about room temperature or below. Instead of using acetone, other solvents, such as ether, etc., 50

may be used.

Upon further and more complete reaction of the ketene with the tartaric acid mentionedin the above example, the carboxyl groups combine with the ketene to form a mix d ester anhydride of II tartaric acid and acetic acid. If this mixed ester anhydride is subjected to heat treatment, for example, at a temperature above 130 .C., the acetone or other .neutral solvent used is volatilized and may be condensed and it is found that the remaining liquid is now a mixture of acetic anhydride and an ester 'anhydride of the original tartaric acid used. These two anhydrides may be separated by distillation by taking of! the acetic 1. The process which comprises reacting 'a ketene with an hydroxy aliphatic earboxyiic acid, whereby a mixed ester anhydride' is obtained, the reaction being conducted in anhydrous liquid phase and at a temperature not higher man 5 2. A process according to claim l'in which-the reaction is conducted at about room temperature.

10 anhydride overhead in the form of a vapor and 3- A proce s according to claim 1 in which the condensing it. The acetic ester anhydride of reaction is carried out in the presence of an inert tartaric acid is recovered as bottoms in the dissolvent.

tillation. k -4. The process which comprises reacting, in an- Glycine, which is an amino aliphatic acid hyd us iquid p e a d a a tempe ture not having the formula CHANEL-)COOH, is reacted higher than 100 0-. a y y aliphatic c rwith ketene in a similar manner. Upon heating boxylic acid with an amount of a ketene suiilcient and fractionating of! the acetic anhydride, a resinly t re t w a yd y G p Of h a due is recovered consisting mainly of a diacetylto form an ester acid. amino acetic anhydride having the formula 5. The process which comprises in a (CH-:NHCOCmC0)-.0 .ketene witha carboxylic acid containing a plu- For the sake of illustration, the following list rality of hydroxyl groups, whereby a mixed ester is given showing a number of hydroxy acids and anhydride is obtained, the reaction being conamino acids which may be reacted with a ketene ducted in anhydrous liquid phase and at a temaccording to the method of the present invention: perature not higher than 100 C. a

Acid Formula 'fifigtt'ieis Hy roxy butyric acid c-Hydroxy isobutyric acid.-

Hydrory oaproic aeid Hydroxystearie acid 011B omooon. Tartronicae one 0003).. 'lartaric acid gm 0% ,(00011),. Mallc mi o0 |.OH(0H).COOH. Citricacid coormnhogm) coomoinooon.

Hydroxy benzoic acid (salicylic acid) EOIDC 0 H. Hydroxytoluie acid .BI|(CO0 (OH)CH: Hydroxy naphthoic i goggsm l- 00H. Gallic acid o .0. moon. Glycine (glyeoeoll) ommimooori. 181101116 C4HQ.CH(NHQ)COOH. 0 o-Amino benzoic acid (anthranllle acid) NH,.C.H4.COOH.

- and heterocyclic acids may be used. Acids of' Various other hydroxy and amino aliphatic cyclic these types containing groups which do not react with ketene may also be used.

The temperature at which the ketene. is .ab

sorbed is preferably-around 20 .C. in most casesv as stated above. However, variations are permissible provided that the heat of reaction is not sufilcient to prevent the formation of the de-.

sired compounds. In the stage of separating the products formed by the ketene absorption, a temperature is preferably employed just above that which is suihcient to distill off thelower boiling of the products, leaving the residual products in the still. It is within the scope of the invention, however, to distill over the products and frac- "tionally condense them. Any desired means of further purification of the products may be employed. 1

Instead of using ketene, CHzCO, one may use various homologs thereof, such as methyl ketene,

CI-hCHCO, etc. 4

It will be understood that the foregoing description is merely illustrative of the invention, and that various changes and alternative procedures' and proportions may be adopted within the scope of the appended claims, in which it is my intention to claim all novelty inherent in the invention as broadly as the prior art permits.

I claim:

sponding diacetic ester dianhydride is obtained.

8. The process which comprises reacting ketene with tartaric acid whereby the corresponding diacetic ester dianhydride is obtained, the reaction being conducted in anhydrous liquid phase at a temperature not higher than 100- C.

9. The process which comprises reacting ketene with an acetone solution of tartaric acid under anhydrous conditions at room temperature.

' whereby the corresponding diacetic ester dianhydride is obtained.

. 10. The process which comprises reacting lretene with tartaric acid in anhydrous liquid phase and at a temperature not higher than- 100 C. to form a,mixed ester anhydrid of tartarlc .acid and acetic acid, and heating e latter toobtain acetic anhydride 'and an ester anhydride' of tartaric acid. 1

PETER J. w'mznvicrr. 

